24 



i.e., without any effort, on the part of the bacteriologist, to produce 

 them. 



Andrewes,* working with the four closely related organisms, 

 B. paratyphosus B and C, B. ceftrycke and the Neivport bacillus, 

 found that in ordinary young cultures of undoubted purity 

 there existed side by side two varieties which could be separated 

 by plating out. They differed antigenically in a very pronounced 

 manner. " The one group reacted well with the monospecific 

 serum, .... while they failed to agglutinate at all with 

 the allied group serum. The other group behaved in the 

 reverse manner, agglutinating well with the group serum, 

 though not to its full titre, while they reacted only weakly 

 with the monospecific serum." These differences in agglutin- 

 ability were confirmed by agglutinogenic tests. A serum pre- 

 pared with a " specific " variety was highly selective for specific 

 strains ; whereas a serum prepared with a " non-specific " variety 

 reacted with the homologous strain and with other non-specific 

 strains but " it fails to react with specific strains except the one 

 of its own type, and even here the titre is very low." The differ- 

 ences in agglutinogenic action were the main fact ; the slight 

 degree of overlapping was to be explained " on the supposition 

 " that specific strains contain a small amount of group antigen, 

 " and unspecific strains a small amount of specific antigen." It 

 is of particular interest to note that the only differences found 

 were those which were demonstrable by serological tests. " The 

 " phenomenon had nothing to do with the ' rough ' and ' smooth ' 

 variants described by Arkwright (1921); all the colonies 

 ' were in every other respect alike, and all gave uniformly 

 " turbid broth cultures." Furthermore, Andrewes found that 

 the same phenonenon might occur in the human body. " I had 

 " the opportunity of examining the primary spleen culture 

 " from a woman who had died of iErtrycke infection ; ten colonies 

 " were picked from this plate and equally fell into the two 

 " sharply defined groups." Two other facts are of importance. 

 (1) No intermediate forms occurred; the varieties always fell 

 into one or other of two distinctive groups, the " specific " or 

 the " non-specific." (2) On sub-culture, each type readily 

 changed into the other. " I have at times succeeded in obtaining 

 ' two consecutive broth cultures in which the character was 

 " maintained pure, but far more commonly even the second 

 " broth culture shows a mixture of types, and I have only rarely 

 obtained pure characters on solid media." 

 The above results are clean-cut and are derived from experi- 

 ments which were free from complicating factors. They are 

 consistent with the observations of other workers who have shown, 

 by the use of the absorption method, that individual bacteria in a 

 pure culture may differ from each other antigenically, some being 

 less fully equipped than others in the attributes of complete 

 specificity. For example, F. Griffith states in the preceding 



* Journ. Path, and Bact., XXV., p. 505, 1922. 



